add close button on right top corner of alert dialog box for android

1<?xml version="1.0" encoding="utf-8"?>
2<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
3    android:layout_width="match_parent"
4    android:layout_height="wrap_content">
5
6    <RelativeLayout
7        android:layout_width="match_parent"
8        android:layout_height="400dp"
9        android:layout_alignParentTop="true"
10        android:layout_marginLeft="10dp"
11        android:layout_marginRight="10dp"
12        android:layout_marginTop="15dp"
13        android:background="#F4F4F4">
14
15        <!--Main Body of your custom dialog-->
16    </RelativeLayout>
17
18    <LinearLayout
19        android:id="@+id/llTop"
20        android:layout_width="wrap_content"
21        android:layout_height="wrap_content"
22        android:layout_alignParentRight="true"
23        android:layout_alignParentTop="true"
24        android:orientation="vertical">
25
26        <ImageButton
27            android:id="@+id/btnCancel"
28            android:layout_width="wrap_content"
29            android:layout_height="wrap_content"
30            android:layout_below="@+id/btnBookK"
31            android:background="@null"
32            android:src="@drawable/ic_close" />
33
34    </LinearLayout>
35
36</RelativeLayout>
37